This document sets forth background materials on the scientific research supporting examinations as conducted by the forensic laboratories at the Department of Justice. It also includes a discussion of significant policy matters. This document is provided to assist a public review and comment process of the related Proposed Uniform Language for Testimony and Reports (posted separately). It is not intended to, does not, and may not be relied upon to create any rights, substantive or procedural, enforceable by law by any party in any matter, civil or criminal, nor does it place any limitation on otherwise lawful investigative and litigative prerogatives of the Department. SUPPORTING DOCUMENTATION FOR DEPARTMENT OF JUSTICE PROPOSED UNIFORM LANGUAGE FOR TESTIMONY AND REPORTS FOR THE FORENSIC HAIR EXAMINATION DISCIPLINE Background Hairs are threadlike outgrowths from the skin of mammals which consist primarily of dead, keratinized cells. Once shed or removed, these hairs may transfer directly or indirectly from one location to another. Questioned hairs recovered from an item can be microscopically examined to determine human or animal (non-human) origin, characteristics of ancestry, somatic origin, artificial treatment, damage, decomposition, and growth stage. Moreover, microscopic comparisons of hair characteristics may determine if a person can or cannot be included as a possible source of a questioned hair.1 However, microscopic comparison of hairs cannot be a basis for personal identification. Following microscopic comparison, human hairs that are associated microscopically are assessed for DNA analysis. Hairs with apparent tissue at the root end and/or hairs in the active growth phase (anagen) are designated for nuclear DNA analysis. Hairs in the resting phase (telogen) with no adhering tissue and hairs without a root are designated for mitochondrial DNA analysis.2 Principles of Forensic Hair Examination When conducting hair comparisons, the examiner assesses the microscopic characteristics of the hair evidence in order to come to a conclusion. An examiner may analyze hairs microscopically to determine somatic origin, characteristics of ancestry, animal (non-human) hair classification, growth stage, damage, artificial treatment, characteristics of decomposition, and suitability for comparison. Depending on the microscopic characteristics that are present, an examiner can come to one of three conclusions regarding the comparison of a questioned hair to a known hair sample: inclusion, exclusion, or inconclusive. Additionally, examiners need to be aware that the science of microscopic hair comparison does not support statements of individualization, statistical weight, or zero error rate. 1 Robertson, J. (1999), Forensic Examination of Hairs, London: Taylor and Francis; see also Oien, C.T. (2009), Forensic Hair Comparison: Background Information for Interpretation, Forensic Science Communications, Volume 11, Number 2; and, Scientific Working Group on Materials Analysis (SWGMAT), Forensic Human Hair Examination Guidelines, Forensic Science Communications, Apr. 2005, vol. 7, no. 2, Section 14. 2 Scientific Working Group on Materials Analysis (SWGMAT) (2005), Forensic Human Hair Examination Guidelines, Forensic Science Communications, vol. 7, no. 2, section 11. 1 Theory of Microscopic Hair Examination The microscopic examination of hairs relies on differences in morphology to classify and distinguish hairs. There are two main regions of a hair, the shaft and the root. The root of the hair lies in the follicle, extending through most of the dermis layer of the skin.3 The shaft of the hair is made of three layers called the cuticle, cortex, and medulla (see Figure 1). The cuticle surrounds the exterior of the hair and is composed of overlapping scales. Underneath the cuticle is the main body of the hair known as the cortex. The cortex contains pigment granules that provide color, small air pockets called cortical fusi, and opaque structures known as ovoid bodies. The inner most layer of cells located near the core of the hair is the medulla. Documented variations in the presence, distribution, appearance, and arrangement of the characteristics described above is the basis for microscopic hair examinations and comparisons.4 Figure 1: Microscopic layers of the hair shaft. Microscopic examination of hairs has been used in criminal investigations since the late 1800s. The first human hair case was reported in Germany in 1861 by Rudolf Virchow. 5 Since this time, numerous publications have described the microscopic characteristics of hairs in detail, including the reliability of using the characteristics to distinguish between individuals.6 In a 3 Marieb, E. N., Hoehn, K. (2010). Human Anatomy & Physiology, Eighth Edition, Pearson Education, Inc., pp157- 159. 4 Robertson, J. (1999), Forensic Examination of Hairs, London: Taylor and Francis; Scientific Working Group on Materials Analysis (SWGMAT) (2005), Forensic Human Hair Examination Guidelines, Forensic Science Communications, vol. 7, no. 2., Section 10; Bisbing R. (2002). The Forensic Identification and Association of Human Hair; In Saferstein R (Ed): Forensic Science Handbook, Vol 1, 2nd ed; Prentice-Hall: Englewood Cliffs, NJ. 5 Bisbing R. (2002). The Forensic Identification and Association of Human Hair; In Saferstein R (Ed): Forensic Science Handbook, Vol 1, 2nd ed; Prentice-Hall: Englewood Cliffs, NJ. 6 Hausman, L. (1944). Applied Microscopy of Hair. The Scientific Monthly, LIX, 195-202. See also Hicks, J. W. (1977). Microscopy of Hairs: A Practical Guide and Manual. Federal Bureau of Investigation, U.S. Government 2 1934 publication entitled “Histological Variability of Human Hair”, Dr. Leon Hausman stated the following: From the results of studies noted in this paper recently made by the writer, and here described, it would appear that a) certain microscopic structural elements in the hair shaft are relatively fixed in their correlations, and b) others appear to be individual enough to be usable as criteria for personal identification.7 Studies have demonstrated how variation in hair morphology between individuals provides meaningful comparisons when utilizing comparison microscopy. A blind study by Strauss8 demonstrated that comparison microscopy correctly associated 100 questioned hairs to the 100 known hair samples. In addition, all 100 questioned hairs were correctly characterized into the appropriate racial classification. A series of studies performed by Gaudette in the 1970s9 demonstrated that both head hairs and pubic hairs could be reliably distinguished from one another. In the head hair studies, a total of 370,230 intercomparisons were conducted, with only nine pairs of hairs that could not be distinguished. In the pubic hair studies, a total of 102,831 intercomparisons were conducted, with only sixteen pairs of hairs that could not be distinguished. In these studies, Gaudette developed a probability estimate for head hair and pubic hair comparisons. In a later study, Gaudette10 stated that “the significance of this research is not in the actual probability numbers found but in experimental proof of the proposition that macroscopic and microscopic hair comparison is a useful technique and that hair evidence is good evidence.” In this study, he provided a single known head hair sample and 100 questioned hairs to examiner trainees. Two of the trainees correctly associated the correct questioned hair to the known sample, and the third examiner trainee found three questioned hairs to be similar to the known sample. In the second part of this study, Gaudette provided a single questioned hair and 100 known hair samples to examiner trainees. Two of the examiner trainees correctly associated the questioned hair to the correct known sample, and the third examiner trainee associated the questioned hair to the correct known hair sample and to one additional known hair sample. Bisbing et al. further demonstrated how the method can also be used to distinguish between 11 twins. In one study, he obtained head hair samples from 17 pairs of twins and one set of Printing Office, Washington D.C.; and Robertson, J. (1999), Forensic Examination of Hairs, London: Taylor and Francis. 7 Hausman. L. (1934). Histological Variability of Human Hair, American Journal of Physical Anthropology, XVIII, 415-428. 8 Strauss, M.T. (1983). Forensic characterization of human hair. The Microscope, 31, 15-29. 9 Gaudette, B. D., Keeping, E. S. (1974). An attempt at determining probabilities in human scalp hair comparisons. Journal of Forensic Sciences, 19, 599-606; Gaudette, B. D. (1976). Probabilities and Human Pubic Hair Comparisons. Journal of Forensic Science, 21, 514-517. 10 Gaudette, B. D. (1978). Some further thoughts on probabilities and human hair comparisons. Journal of Forensic Sciences 23, 758–763. 11 Bisbing, R. E., Wolner, M. F. (1984). Microscopical Discrimination of Twins’ Head Hair. Journal of Forensic Sciences, 29, 780-786. 3 triplets. In the first part of this study, duplicate hair samples from each twin were compared. The researchers were able to pair each hair sample to its correct duplicate sample without any incorrect associations or exclusions. The second part of this study was designed to simulate forensic case work, where seven separate questioned hairs were compared to several randomly selected known samples obtained from the twins or triplets. In the seven tests, one examiner correctly excluded 47 out of 52 samples, and a second examiner correctly excluded 49 out of 52 samples.